Ozone is an unstable triatomic allotrope of oxygen. It is produced in an energized environment wherein molecular oxygen dissociates into monatomic oxygen which subsequently collides and recombines with an oxygen molecule to form a highly reactive ozone molecule.
Although ozone is primarily employed in disinfection, it can perform other functions such as color reduction, odor and taste removal, algae control, oxidation of inorganic and organic compounds in water and waste-water treatment practices, waste gas treatment and bleaching of paper pulp.
The most prominent features of ozone as a biocide lie in its speed and selectivity in oxidation. Biocidal effects are believed to primarily be achieved through oxidation. Consistent with this belief, the ability of any chemical to reduce microbial viability is in direct proportion to its oxidation potential. Ozone is the fourth most powerful oxidizing agent known; only fluorine, fluorine dioxide, and monatomic oxygen are thought to be more reactive. Ozone possesses an oxidation potential of 2.07 millivolts relative to chlorine gas' 1.36 millivolts. It is important to note that an increased oxidation potential is indicative of an accelerated bacterial kill. The rate of disinfection has been demonstrated to be more than 3,000 times faster than chlorine; thus contact time is a lesser consideration in the application of ozone as a microbicide.
Disinfection with the use of ozone may proceed by oxidation directly and by intermediate hydroperoxy compounds that can interact with cytosolic components. Organic ozone chemistry would predict that oxidized organic compounds containing carbon-carbon double bonds give rise to hydroperoxyalcohols. Evidence exists that organic peroxides exert a stronger bacteriocidal action than hydrogen peroxide due to a greater tendency to decompose. No evidence is believed to exist in the literature of any microorganism that is resistant to the effects of ozone exposure. The application of ozone is preferable due to its compatibility with biota. There are no residual or harmful reaction products downstream, particularly in the range of 0-20 ppm. The presence of peroxidic compounds could be perceived to be harmful to the biota, but toxicity studies indicate the contrary to be true. Studies have shown that these compounds are chemically highly unstable and rapidly decompose. It has also been shown that these compounds can be removed by other oxidizing molecules.
This information is in juxtaposition with information generated regarding the toxic effects of chorine and chlorinated products on the general biota, as well as on human life. There is some substantiation to the claim that dioxin, a by-product of chlorine, may be linked to cancer and diseases of the human immunological, developmental and reproductive functions.
In addition to demonstrating powerful capabilities in the destruction or inactivation of bacteria, fungi and protozoa; ozone has been shown to be virucidal. The efficacy of ozone has been reported to range from (all of the following values given reported a 99% reduction) 2.2 mg/l for Escherichia coli in 19 minutes from raw waste water; 0.02 mg/l for Candida tropicalis in 0.30 minutes from ozone-demand free water; 1.2 mg/l for Naegleria gruberi in 1.1 minutes from ozone-demand free phosphate buffer solution and 0.2 mg/l for Poliovirus type I in 9 minutes from activated sludge effluent. With regard to bacterial spores (specifically, Bacillus subtilis v. globigii), ozone has been shown to achieve a four-log reduction within 1.5-2 minutes when water is purged with 3% ozone by weight. Using a non-toxic concentration of 4 .mu.g ozone per ml of serum, ozone can achieve a six-log reduction in the infectious titer of human immunodeficiency virus ("HIV").
Presently, the most commonly employed method of "bioburden" reduction within the washwheel is chlorination. The most actively oxidative form of chlorine, formed by the hydrolysis of chlorine in water, is hypochlorite hypochlorous acid. Studies have shown ozone to be more powerful by factors ranging between 5-1000. Both chemicals limit outgrowth, inactivate or destroy microbes via oxidation, but unlike chlorine, ozone's action is more direct, faster and engenders fewer residual considerations. The half-life of ozone in solution is less than 30 minutes and it is highly susceptible to degradation by increased temperature, pH and photolysis by ultraviolet light whereas chlorine generates chlorinated organic compounds which present more of a challenge with regard to removal or neutralization. The application of ozone in disinfection, sanitization or sterilization processes results in improved wastewater quality.
Currently, such as in hospital operating rooms, many garments are disposed of to facilitate containment of bloodborne pathogens, as well as other infectious agents. Reuse of these items constitutes an immense saving in capital expenditures; regarding purchase of single-use items and their biohazardous disposal costs, as well as demonstrating environmental responsibility. Reuse of these items generates special consideration for laundry personnel. In this environment, the necessity for a reliable means of reducing the bioburden to acceptable levels is of critical importance.
It would be an improvement in the art to have a relatively economical, reliable method of disinfecting, sanitizing or sterilizing textiles such as garments or healthcare linens.